Cellulose organic acid ester plastics containing hydroquinone monosalicylate



United States Patent CELLULOSE ORGANIC ACID ESTER PLASTICS CONTAINING HYDROQUINONE MONO- SALICYLATE Lester W. A. Meyer and Margaret H. Broyles, Kingsport,

Tenn., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application April 13, 1954 Serial No. 422,982

3 Claims. (Cl. 106-182) This invention relates to cellulose organic acid ester plastics, and more particularly to the stabilization of such plastics.

As is well known in the art, plastics having excellent properties for a great many purposes can be prepared from cellulose organic acid esters, such, for example, as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate and cellulose acetate-butyrate, with suitable plasticizers. Many examples of suitable plasticizers are shown in the art. The choice of plasticizers forms no part of our invention.

However, cellulose organic acid ester plastics have not been entirely suitable for use in places where they are exposed to a considerable amount of ultraviolet light: e. g., out of doors. After one or two months of outdoor exposure in a sunny climate, the plastic bleached and became increasingly brittle until, at the end of from three to six months, depending on the severity of the climate, crazing occurred. The rapid deterioration of appearance was accompanied by an equally rapid breakdown in physical properties, such as strength.

We have found that the addition of a small proportion of hydroquinone monosalicylate OH 0 ll to a cellulose organic acid ester plastic composition strongly inhibits breakdown of the resulting plastic by exposure to ultraviolet light. We prefer to use approximately 0.5% to 5.0% of hydroquinone mono-salicylate, based on the weight of cellulose organic acid ester. Higher amounts give only slightly greater weathering resistance, and may change the physical properties of the plastic. As cellulose organic acid'esters, we have employed those mentioned above, in which the acyl groups contain from 2 to 4 carbon atoms. Cellulose acetate plastics are not as efiective for outdoor uses as are the mixed and higher esters, that is, those containing an acyl group higher than acetyl, because the usual cellulose acetate plasticizer retention is rather poor under outdoor exposure.

Hydroquinone monosalicylate imparts a slight color to the cellulose organic ester plastic, and this color intensifies somewhat on exposure, but it is suitable for use in dark colored plastics, which have many outdoor uses.

In testing our cellulose organic acid ester plastics containing hydroquinone monosalicylate, we have tested sheets of 0.050" thickness by the Kline test, designated as A. S. T. M. D795-49. The method consists of the following test cycle:

18 hours under General Electric S-1 sunlamp (6 inches below lamp) 2 hours in fog chamber 2 hours under S-l sunlamp 2 hours in fog chamber This cycle was repeated until the first sign of surface failure of the samples of plastic, as shown by dulling, chalking, checking, crazing, or warping. The temperature inside the accelerated Weathering machine is maintained at 55 to 60 C.

-It has been found by the National Bureau of Standards and verified by us, that roughly 200 hours sunlamp exposure by this test is equivalent to one years outdoor exposure in Washington, D. C. Outdoor exposure farther south or at high altiude is more severe, however.

The following table shows the values obtained by weathering similar samples of plasticized cellulose acetatebutyrate plastics of the same compositions, containing (a) no ultraviolet inhibitor, (b) 1%, based on the cellulose ester, of the well-known ultraviolet inhibtor,

The numbers in the color of plastic column indicate the relative intensity of coloration of the samples.

At the end of 1790 hours, the sample containing the hydroquinone mono-salicylate showed slight, fine crazing of the surface.

Hydroquinone mono-salicylate is advantageously introduced into a cellulose organic acid ester plastic at the time the cellulose ester is compounded with the plasticizer. This compounding may be accomplished by any of the known methods, including the method of working on hot rolls described in Conklins U. S. Patent 2,155,303.

By way of application, we give the following example of making up cellulose organic acid ester plastics containing hydroquinone mono-salicylate. It will be understood that this illustration does not constitute a limitation of our invention, which is defined in the appended claims.

Example. parts of cellulose acetate-butyrate containing approximately 12% acetyl and 37% butyryl is intimately mixed in a sigma-blade mixer with 13 parts of dibutyl sebacate and 1 part of hydroquinone monosalicylate. The mixture is Worked on hot rolls by the method described in the Conklin Patent 2,155,303. The resulting plastic can then be granulated and be ready for any molding or extrusion operation.

Any of the known plasticizers for cellulose organic acid esters, such, for example, as dibutyl phthalate, dibutyl sebacate, methoxyethyl stearate, tricresyl phosphate, butoxyethyl phthalate, diamyl phthalate, ethyl ptoluene sulfonamide, etc. may be used. In the case of the softer cellulose esters, such as cellulose acetatebutyrate, plastics may even be formed without the use of any plasticizer.

What we claim as our invention and desire to be secured by Letters Patent of the United States is:

1. A cellulose organic acid ester plastic comprising a cellulose organic acid ester selected from the group consisting of cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate and cellulose acetate-butyrate, a plasticizer therefor, and, as an agent for inhibiting deterioration of the plastic by ultraviolet light, approximately 0.5% to 5%, based on the weight of the cellulose ester, of hydroquinone mono-salicylate.

2. A cellulose acetate-butyrate plastic comprising cellulose acetate-butyrate, a plasticizer therefor, and, as an agent for inhibiting deterioration of the plastic by ultra- References Cited in the file of'this patent UNITED STATES PATENTS 2,264,291 Boyer et al. Dec. 2, 1941 4 Koch Nov. 20, 1945 Swan Sept. 3, 1946 Dreyfus Dec. 16, 1947 Simpson et a1. Nov. 30, 1948 Meyer et al. Apr. 8, 1952 Wynn et a1 Aug. 17, 1954 FOREIGN PATENTS Great Britain Sept. 22, 1938 

1. A CELLULOSE ORGANIC ACID ESTER PLASTIC COMPRISING A CELLULOSE ORGANIC ACID ESTER SELECTED FROM THE GROUP CONSISTING OF CELLULOSE ACETATE, CELLULOSE PROPIONATE, CELLULOSE BUTYRATE, CELLULOSE ACETATE-PROPIONATE AND CELLULOSE ACETATE-BUTYRATE, A PLASTICIZER THEREOF, AND, AS AN AGENT FOR INHIBITING DETERIORATION OF THE PLASTIC BY ULTRAVIOLET LIGHT, APPROXIMATELY 0.5% TO 5%, BASED ON THE WEIGHT OF THE CELLULOSE ESTER, OF HYDROQUINONE MONO-SALICYCLATE. 